Sooty terns

On Location: A Wildlife Spectacle on Malden Island

Shirley Metz|September 11, 2008|Blog Post

Malden and Starbuck Islands are the northernmost islands of the southern part of the Line Islands in the Republic of Kiribati. Both Malden and Starbuck are coral atolls and were mined extensively from the late 1800s until the early 1900s for phosphates. Phosphate deposits are guano deposited by seabirds over the countless years that the islands have stood above the surface of the sea. Used for fertilizers and during WWII for explosives, guano contains about 11 to 16 percent nitrogen, 8 to 12 percent phosphoric acid, and 2 to 3 percent potash. In 1957 Malden, together with Kiritimati, was used as a site for the development of nuclear weapons as part of Britain’s Operation Grapple.

Malden is the second largest member of the Line Islands. At the center of the island, the highest point of which is 25 feet above sea level, is a low shallow lagoon which contains numerous small islets and ridges composed of coral rubble. The lagoon is not connected to the open ocean; instead water exchange takes place through subterranean fissures. It is beneath the lagoon waters that an estimated 25-30-million tons of unconsolidated articulate gypsum is believed to lie. The Kiribati government has undertaken feasibility studies to assess the extraction of the island’s gypsum deposits. However, as with the other uninhabited islands of the southern group, Malden is protected as a Wildlife Sanctuary and Closed Area. It is an important breeding island for gray-backed terns (sterna lunata), red-tailed tropicbirds (phaethon rubricauda melanorhynchos), and lesser frigatebirds (fregata ariel). Nine other species are also known to breed on the island including sooty terns (sterna fuscata.) It is also an important winter-stop for the bristle-thighed curlew (numenius tahitiensis), a migrant from Alaska. This latter species is now threatened due to habitat destruction.

When we landed on Malden we saw scattered throughout the island the remains of the guano industry – lava-stone remnants of buildings, rusting hulks of machinery, and decaying debris, some 50 years old or more. One would hardly expect to find this mess on a Wildlife Sanctuary island, but hey, the birds take what they can get. With conservation funding and will on the part of Kiribati government, the “trashed” areas of the island could be cleaned up and restored to a more pristine state. To mine the gypsum would be inexcusable and would destroy this precious habitat. We were dismayed to find a pathetic-looking black cat on the island beneath the red-footed booby nests. There were several bird bones at the base of the shrubs and the cat looked to be the guilty culprit. We attempted to catch the cat but it proved too wily for us ill-equipped cat-catchers. The unfortunate aspect of the presence of a cat on such a remote island is that it is unlikely that this is a 50-year-old cat. There are most likely more feral cats on the island with which it breeds. Cats can quickly decimate an entire species of bird.

Upon departing Malden, I asked the Captain if he could take the Clipper Odyssey along the eastern coast of the island. It was dusk and as we looked up into the cloud-filled skies our jaws dropped in amazement. What could only have been described as a wildlife spectacle was happening before our very eyes. It has most likely only been witnessed by a handful of humans – and we at this moment were the chosen few.

Not hundreds, not thousands, but thousands upon thousands of sooty terns – 50,000, maybe 100,000 – they have not been counted - filled the skies. I thrust my binoculars into the Captain’s hands and told him to look. Not an avid naturalist, he asked what was this locust event that was darkening the skies?

The sooty tern fishes at sea upon fish and squid, hovering over the ocean surface and diving in pursuit of its prey. Nesting colonies are active from February through September after which the birds depart for the open sea. It prefers to nest on flat, sandy areas where one speckled egg is laid amongst huge nesting colonies. We were witnessing their commute home as the birds were returning to Malden Island having been at sea for the day feeding. It was an unbelievable climax to an unbelievable day here in the Line Islands!

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